Electronics > Beginners

Analyzing and Understanding Waveforms on a TENS Unit

(1/7) > >>

JJ_023:
Need guidance in analyzing and understanding waveforms on a Transcutaneous Electrical Nerve Stimulation machine (TENS Unit).

I am asking the community to chime in and expand my understanding as well as learn a few things along the way.

I was playing with a TENS unit.  The unit is a medically prescribed unit.  I was curious about the parameters and what the actual unit put out.  Here are my findings. 

Maxed out the unit produces around 20V AC and 9.4 µA of current.  I used a fluke 87 V for this.

When I tried reading the Hz the meter was not capable.  This made me want to throw the unit on a scope and see the waveform.  This completely blew me away.  300+ volts peak to peak.  See the attached two images of the waveform I captured.

This particular unit has two adjustments.  One is called “PULSE RATE” which is actually the Hz.  It tops out at around 150 Hz and was accurately calibrated to the device.
The other control is called “Pulse Width”, which can be thought of as the duty cycle, but is labeled in a very confusing manner.

Why was the Fluke unable to read the Hz?  My guess is that the duty cycle was too low.

Could this waveform be re-created utilizing a signal generator from some of the Rigol or Siglent lower tier units that are around $600?  If not what would it take to re-create this type of signal?

Can this really put out 300 V peak to peak or am I misinterpreting something?

As usual thank you to anybody that comments or participates in this discussion.

Kim Christensen:
Just need to pulse a coil/transformer to get some high voltage spikes. Simple 555 timer IC, or other pulse generator, driving a transistor which drives the primary of the transformer. The only difficult part is making the intensity the right level so it's not harmful or painful. Experiment on yourself first. ;)
Essentially, it's a very low power TASER..  >:D

ejeffrey:
I don't know anything about TENS or this circuit but 300 v pk-pk as measured by a scope probe sounds reasonable.  It takes a fair bit of voltage to get through the skin even for a small current.  However the available current / energy will be limited to a (hopefully) safe level.  In actual use the voltage will probably be lower due to the loading by the user.

You can't just program an AWG to make the waveform you see, that would be unsafe.

JJ_023:

--- Quote from: Kim Christensen on June 20, 2024, 12:01:10 am ---Just need to pulse a coil/transformer to get some high voltage spikes. Simple 555 timer IC, or other pulse generator, driving a transistor which drives the primary of the transformer. The only difficult part is making the intensity the right level so it's not harmful or painful. Experiment on yourself first. ;)
Essentially, it's a very low power TASER..  >:D

--- End quote ---

Thank you for your input.   From my experience 555 circuits don't produce this type of waveform, so I am not sure how to do that.   There is also a negative aspect to this waveform that is not uniform.

JJ_023:

--- Quote from: ejeffrey on June 20, 2024, 01:33:26 am ---I don't know anything about TENS or this circuit but 300 v pk-pk as measured by a scope probe sounds reasonable.  It takes a fair bit of voltage to get through the skin even for a small current.  However the available current / energy will be limited to a (hopefully) safe level.  In actual use the voltage will probably be lower due to the loading by the user.

You can't just program an AWG to make the waveform you see, that would be unsafe.

--- End quote ---

TENS units can be used for a lot of things such as nerve and muscle stimulation.  My question is why can't you program an AWG?   What would be unsafe about it?  The AWG is a much more Robust and precise piece of equipment then a TENS unit.

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod